cat.c

   1 /* baseutils: `cat.c` - con`cat`enate and print files.
   2    Copyright (c) 2022, Yusuf
   3    See `LICENSE` for copyright and license details */
   4
   5 #define _POSIX_C_SOURCE 200809L
   6
   7 #ifdef __linux__
   8 /* for splice() support */
   9 #define _GNU_SOURCE
  10 #endif
  11
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <errno.h>
  15 #include <string.h>
  16 #include <unistd.h>
  17 #include <fcntl.h>
  18 #include <sys/param.h>
  19 #include <sys/stat.h>
  20
  21 static const char *usage = "cat [-u] [file...]";
  22
  23 /* amount of bytes to transfer in one iteration */
  24 #define BUF_SIZE 16384
  25
  26 void
  27 cat(int file_fd)
  28 {
  29         static char* buffer = NULL;
  30         static int buf_sz = 0;
  31         int n_bytes;
  32         struct stat sbuf;
  33
  34         if (!buffer) {
  35                 if (fstat(file_fd, &sbuf) < 0) {
  36                         perror("uname");
  37                         exit(1);
  38                 }
  39
  40                 buf_sz = MAX(BUF_SIZE, sbuf.st_blksize);
  41                 if ((buffer = malloc(buf_sz)) == NULL) {
  42                         perror("malloc");
  43                         exit(1);
  44                 }
  45         }
  46
  47
  48         for (;;) {
  49                 n_bytes = read(file_fd, (void *)buffer, buf_sz);
  50                 if (n_bytes <= 0)
  51                         break;
  52
  53                 write(fileno(stdout), buffer, n_bytes);
  54         }
  55 }
  56
  57 #ifdef __linux__
  58 void
  59 fastcat(int file_fd)
  60 {
  61         int result;
  62
  63         for(;;) {
  64                 // we make the assumption here that
  65                 // STDOUT_FD == 1, which is true on linux...
  66                 result = splice(file_fd, NULL, 1, NULL, BUF_SIZE * 4, 0);
  67                 if (result >= 0)
  68                         break;
  69         }
  70 }
  71 #else
  72 #define fastcat(fd) cat(fd)
  73 #endif
  74
  75 int
  76 process_file(const char* name, int unbuf)
  77 {
  78         int fd;
  79
  80         if (strcmp(name, "-") == 0) {
  81                 if (unbuf)
  82                         if (setvbuf(stdin, NULL, _IONBF, 0) == EOF)
  83                                 fputs("cat: -u: unbuffer request failed\n", stderr);
  84
  85                 fd = fileno(stdin);
  86         } else {
  87                 fd = open(name, O_RDONLY);
  88         }
  89
  90         if (fd < 0) {
  91                 return EXIT_FAILURE;
  92         } else if (!isatty(fd)) {
  93                 fastcat(fd);
  94         } else {
  95                 cat(fd);
  96         }
  97
  98         return EXIT_SUCCESS;
  99 }
 100
 101 int
 102 main(int argc, char *argv[])
 103 {
 104         char ch;
 105         int status, i, u, fd;
 106
 107         status = EXIT_SUCCESS;
 108
 109         while ((ch = getopt(argc, argv, "u")) != -1) {
 110                 switch (ch) {
 111                 case 'u':
 112                         if (setvbuf(stdout, NULL, _IONBF, 0) == EOF)
 113                                 fputs("cat: -u: unbuffer request failed\n", stderr);
 114                         u = 1;
 115                         break;
 116                 case '?':
 117                 default:
 118                         fprintf(stderr, "Usage:\n\t%s\n", usage);
 119                         return EXIT_FAILURE;
 120                 }
 121         }
 122
 123         argv += optind;
 124         argc -= optind;
 125
 126         if (argc < 1) {
 127                 // stdin only
 128                 return process_file("-", u);
 129         }
 130
 131         for (i = 0; i < argc; i++) {
 132                 status = process_file(argv[i], u);
 133         }
 134
 135         return status;
 136 }